@phdthesis{1127, abstract = {Plant hormone auxin and its transport between cells belong to the most important mechanisms controlling plant development. Auxin itself could change localization of PINs and thereby control direction of its own flow. We performed an expression profiling experiment in Arabidopsis roots to identify potential regulators of PIN polarity which are transcriptionally regulated by auxin signalling. We identified several novel regulators and performed a detailed characterization of the transcription factor WRKY23 (At2g47260) and its role in auxin feedback on PIN polarity. Gain-of-function and dominant-negative mutants revealed that WRKY23 plays a crucial role in mediating the auxin effect on PIN polarity. In concordance, typical polar auxin transport processes such as gravitropism and leaf vascular pattern formation were disturbed by interfering with WRKY23 function. In order to identify direct targets of WRKY23, we performed consequential expression profiling experiments using a WRKY23 inducible gain-of-function line and dominant-negative WRKY23 line that is defunct in PIN re-arrangement. Among several genes mostly related to the groups of cell wall and defense process regulators, we identified LYSINE-HISTIDINE TRANSPORTER 1 (LHT1; At5g40780), a small amino acid permease gene from the amino acid/auxin permease family (AAAP), we present its detailed characterisation in auxin feedback on PIN repolarization, identified its transcriptional regulation, we propose a potential mechanism of its action. Moreover, we identified also a member of receptor-like protein kinase LRR-RLK (LEUCINE-RICH REPEAT TRANSMEMBRANE PROTEIN KINASE PROTEIN 1; LRRK1; At1g05700), which also affects auxin-dependent PIN re-arrangement. We described its transcriptional behaviour, subcellular localization. Based on global expression data, we tried to identify ligand responsible for mechanism of signalling and suggest signalling partner and interactors. Additionally, we described role of novel phytohormone group, strigolactone, in auxin-dependent PIN re-arrangement, that could be a fundament for future studies in this field. Our results provide first insights into an auxin transcriptional network targeting PIN localization and thus regulating plant development. We highlighted WRKY23 transcriptional network and characterised its mediatory role in plant development. We identified direct effectors of this network, LHT1 and LRRK1, and describe their roles in PIN re-arrangement and PIN-dependent auxin transport processes.}, author = {Prat, Tomas}, issn = {2663-337X}, pages = {131}, publisher = {Institute of Science and Technology Austria}, title = {{Identification of novel regulators of PIN polarity and development of novel auxin sensor}}, year = {2017}, } @phdthesis{839, abstract = {This thesis describes a brittle fracture simulation method for visual effects applications. Building upon a symmetric Galerkin boundary element method, we first compute stress intensity factors following the theory of linear elastic fracture mechanics. We then use these stress intensities to simulate the motion of a propagating crack front at a significantly higher resolution than the overall deformation of the breaking object. Allowing for spatial variations of the material's toughness during crack propagation produces visually realistic, highly-detailed fracture surfaces. Furthermore, we introduce approximations for stress intensities and crack opening displacements, resulting in both practical speed-up and theoretically superior runtime complexity compared to previous methods. While we choose a quasi-static approach to fracture mechanics, ignoring dynamic deformations, we also couple our fracture simulation framework to a standard rigid-body dynamics solver, enabling visual effects artists to simulate both large scale motion, as well as fracturing due to collision forces in a combined system. As fractures inside of an object grow, their geometry must be represented both in the coarse boundary element mesh, as well as at the desired fine output resolution. Using a boundary element method, we avoid complicated volumetric meshing operations. Instead we describe a simple set of surface meshing operations that allow us to progressively add cracks to the mesh of an object and still re-use all previously computed entries of the linear boundary element system matrix. On the high resolution level, we opt for an implicit surface representation. We then describe how to capture fracture surfaces during crack propagation, as well as separate the individual fragments resulting from the fracture process, based on this implicit representation. We show results obtained with our method, either solving the full boundary element system in every time step, or alternatively using our fast approximations. These results demonstrate that both of these methods perform well in basic test cases and produce realistic fracture surfaces. Furthermore we show that our fast approximations substantially out-perform the standard approach in more demanding scenarios. Finally, these two methods naturally combine, using the full solution while the problem size is manageably small and switching to the fast approximations later on. The resulting hybrid method gives the user a direct way to choose between speed and accuracy of the simulation. }, author = {Hahn, David}, issn = {2663-337X}, pages = {124}, publisher = {Institute of Science and Technology Austria}, title = {{Brittle fracture simulation with boundary elements for computer graphics}}, doi = {10.15479/AT:ISTA:th_855}, year = {2017}, } @misc{5568, abstract = {Includes source codes, test cases, and example data used in the thesis Brittle Fracture Simulation with Boundary Elements for Computer Graphics. Also includes pre-built binaries of the HyENA library, but not sources - please contact the HyENA authors to obtain these sources if required (https://mech.tugraz.at/hyena)}, author = {Hahn, David}, keywords = {Boundary elements, brittle fracture, computer graphics, fracture simulation}, publisher = {Institute of Science and Technology Austria}, title = {{Source codes: Brittle fracture simulation with boundary elements for computer graphics}}, doi = {10.15479/AT:ISTA:73}, year = {2017}, } @inproceedings{559, abstract = {Proofs of space (PoS) were suggested as more ecological and economical alternative to proofs of work, which are currently used in blockchain designs like Bitcoin. The existing PoS are based on rather sophisticated graph pebbling lower bounds. Much simpler and in several aspects more efficient schemes based on inverting random functions have been suggested, but they don’t give meaningful security guarantees due to existing time-memory trade-offs. In particular, Hellman showed that any permutation over a domain of size N can be inverted in time T by an algorithm that is given S bits of auxiliary information whenever (Formula presented). For functions Hellman gives a weaker attack with S2· T≈ N2 (e.g., S= T≈ N2/3). To prove lower bounds, one considers an adversary who has access to an oracle f: [ N] → [N] and can make T oracle queries. The best known lower bound is S· T∈ Ω(N) and holds for random functions and permutations. We construct functions that provably require more time and/or space to invert. Specifically, for any constant k we construct a function [N] → [N] that cannot be inverted unless Sk· T∈ Ω(Nk) (in particular, S= T≈ (Formula presented). Our construction does not contradict Hellman’s time-memory trade-off, because it cannot be efficiently evaluated in forward direction. However, its entire function table can be computed in time quasilinear in N, which is sufficient for the PoS application. Our simplest construction is built from a random function oracle g: [N] × [N] → [ N] and a random permutation oracle f: [N] → N] and is defined as h(x) = g(x, x′) where f(x) = π(f(x′)) with π being any involution without a fixed point, e.g. flipping all the bits. For this function we prove that any adversary who gets S bits of auxiliary information, makes at most T oracle queries, and inverts h on an ϵ fraction of outputs must satisfy S2· T∈ Ω(ϵ2N2).}, author = {Abusalah, Hamza M and Alwen, Joel F and Cohen, Bram and Khilko, Danylo and Pietrzak, Krzysztof Z and Reyzin, Leonid}, isbn = {978-331970696-2}, location = {Hong Kong, China}, pages = {357 -- 379}, publisher = {Springer}, title = {{Beyond Hellman’s time-memory trade-offs with applications to proofs of space}}, doi = {10.1007/978-3-319-70697-9_13}, volume = {10625}, year = {2017}, } @article{1144, abstract = {We show that matrix elements of functions of N × N Wigner matrices fluctuate on a scale of order N−1/2 and we identify the limiting fluctuation. Our result holds for any function f of the matrix that has bounded variation thus considerably relaxing the regularity requirement imposed in [7, 11].}, author = {Erdös, László and Schröder, Dominik J}, journal = {Electronic Communications in Probability}, publisher = {Institute of Mathematical Statistics}, title = {{Fluctuations of functions of Wigner matrices}}, doi = {10.1214/16-ECP38}, volume = {21}, year = {2017}, } @article{795, abstract = {We introduce a common generalization of the strong Hanani–Tutte theorem and the weak Hanani–Tutte theorem: if a graph G has a drawing D in the plane where every pair of independent edges crosses an even number of times, then G has a planar drawing preserving the rotation of each vertex whose incident edges cross each other evenly in D. The theorem is implicit in the proof of the strong Hanani–Tutte theorem by Pelsmajer, Schaefer and Štefankovič. We give a new, somewhat simpler proof.}, author = {Fulek, Radoslav and Kynčl, Jan and Pálvölgyi, Dömötör}, issn = {1077-8926}, journal = {The Electronic Journal of Combinatorics}, number = {3}, publisher = {Electronic Journal of Combinatorics}, title = {{Unified Hanani Tutte theorem}}, doi = {10.37236/6663}, volume = {24}, year = {2017}, } @article{22514, abstract = {While the significance of elevated atmospheric CO2 concentration on instantaneous leaf-level processes such as photosynthesis and transpiration is rarely disputed, its integrated effect at ecosystem level and at long-time scales remains a subject of debate. In part, the uncertainty stems from the inherent leaf-to-leaf variability in gas exchange rates. By combining 10 years of leaf gas exchange measurements collected during the Duke Forest Free Air CO2 Enrichment (FACE) experiment and three different leaf-scale stomatal conductance models, the leaf-to-leaf variability in photosynthetic and stomatal conductance properties is examined. How this variability is then reflected in ecosystem water vapor and carbon dioxide fluxes is explored by scaling up the leaf-level process to the canopy using model calculations. The main results are: (a) the space-time variability of the photosynthesis and stomatal conductance response is considerable as expected. (b) Variability of the calculated leaf level fluxes is dependent on both the meteorological drivers and differences in leaf age, position within the canopy, nitrogen and CO2 fertilization, which can be accommodated in model parameters. (c) Meteorological variability is playing the dominant role at short temporal scales while parameter variability is significant at longer temporal scales. (d) Leaf level results do not necessarily translate to similar ecosystem level responses due to indirect effects and other compensatory mechanisms related to long-term vegetation dynamics and ecosystem water balance.}, author = {Paschalis, Athanasios and Katul, Gabriel G. and Fatichi, Simone and Palmroth, Sari and Way, Danielle}, issn = {1873-2240}, journal = {Agricultural and Forest Meteorology}, keywords = {Ecohydrological modeling, Elevated CO2, FACE, Stomatal conductance model, Spatio-temporal variability}, pages = {367--383}, publisher = {Elsevier}, title = {{On the variability of the ecosystem response to elevated atmospheric CO2 across spatial and temporal scales at the Duke Forest FACE experiment}}, doi = {10.1016/j.agrformet.2016.09.003}, volume = {232}, year = {2017}, } @article{22543, abstract = {A new stochastic weather generator, Advanced WEather GENerator for a two-dimensional grid (AWE-GEN-2d) is presented. The model combines physical and stochastic approaches to simulate key meteorological variables at high spatial and temporal resolution: 2 km × 2 km and 5 min for precipitation and cloud cover and 100 m × 100 m and 1 h for near-surface air temperature, solar radiation, vapor pressure, atmospheric pressure, and near-surface wind. The model requires spatially distributed data for the calibration process, which can nowadays be obtained by remote sensing devices (weather radar and satellites), reanalysis data sets and ground stations. AWE-GEN-2d is parsimonious in terms of computational demand and therefore is particularly suitable for studies where exploring internal climatic variability at multiple spatial and temporal scales is fundamental. Applications of the model include models of environmental systems, such as hydrological and geomorphological models, where high-resolution spatial and temporal meteorological forcing is crucial. The weather generator was calibrated and validated for the Engelberg region, an area with complex topography in the Swiss Alps. Model test shows that the climate variables are generated by AWE-GEN-2d with a level of accuracy that is sufficient for many practical applications.}, author = {Peleg, Nadav and Fatichi, Simone and Paschalis, Athanasios and Molnar, Peter and Burlando, Paolo}, issn = {1942-2466}, journal = {Journal of Advances in Modeling Earth Systems}, number = {3}, pages = {1595--1627}, publisher = {American Geophysical Union}, title = {{An advanced stochastic weather generator for simulating 2‐D high‐resolution climate variables}}, doi = {10.1002/2016ms000854}, volume = {9}, year = {2017}, } @article{22488, abstract = {Elevated atmospheric CO2 concentrations are expected to enhance photosynthesis and reduce stomatal conductance, thus increasing plant water use efficiency. A recent study based on eddy covariance flux observations from Northern Hemisphere forests showed a large increase in inherent water use efficiency (IWUE). Here we used an updated version of the same data set and robust uncertainty quantification to revisit these contemporary IWUE trends. We tested the hypothesis that the observed IWUE increase could be attributed to interannual trends in plant functional traits, potentially triggered by environmental change. We found that IWUE increased by ~1.3% yr−1, which is less than previously reported but still larger than theoretical expectations. Numerical simulations with the Tethys-Chloris ecosystem model using temporally static plant functional traits cannot explain this increase. Simulations with plant functional trait plasticity, i.e., temporal changes in model parameters such as specific leaf area and maximum Rubisco capacity, match the observed trends in IWUE. Our results show that trends in plant functional traits, equal to 1.0% yr−1, can explain the observed IWUE trends. Thus, at decadal or longer time scales, trait plasticity could potentially influence forest water, carbon, and energy fluxes with profound implications for both the monitoring of temporal changes in plant functional traits and their representation in Earth system models.}, author = {Mastrotheodoros, Theodoros and Pappas, Christoforos and Molnar, Peter and Burlando, Paolo and Keenan, Trevor F. and Gentine, Pierre and Gough, Christopher M. and Fatichi, Simone}, issn = {2169-8961}, journal = {Journal of Geophysical Research: Biogeosciences}, number = {9}, pages = {2393--2408}, publisher = {American Geophysical Union}, title = {{Linking plant functional trait plasticity and the large increase in forest water use efficiency}}, doi = {10.1002/2017jg003890}, volume = {122}, year = {2017}, } @article{914, abstract = {Infections with potentially lethal pathogens may negatively affect an individual’s lifespan and decrease its reproductive value. The terminal investment hypothesis predicts that individuals faced with a reduced survival should invest more into reproduction instead of maintenance and growth. Several studies suggest that individuals are indeed able to estimate their body condition and to increase their reproductive effort with approaching death, while other studies gave ambiguous results. We investigate whether queens of a perennial social insect (ant) are able to boost their reproduction following infection with an obligate killing pathogen. Social insect queens are special with regard to reproduction and aging, as they outlive conspecific non-reproductive workers. Moreover, in the ant Cardiocondyla obscurior, fecundity increases with queen age. However, it remained unclear whether this reflects negative reproductive senescence or terminal investment in response to approaching death. Here, we test whether queens of C. obscurior react to infection with the entomopathogenic fungus Metarhizium brunneum by an increased egg-laying rate. We show that a fungal infection triggers a reinforced investment in reproduction in queens. This adjustment of the reproductive rate by ant queens is consistent with predictions of the terminal investment hypothesis and is reported for the first time in a social insect.}, author = {Giehr, Julia and Grasse, Anna V and Cremer, Sylvia and Heinze, Jürgen and Schrempf, Alexandra}, issn = {2054-5703}, journal = {Royal Society Open Science}, number = {7}, publisher = {Royal Society}, title = {{Ant queens increase their reproductive efforts after pathogen infection}}, doi = {10.1098/rsos.170547}, volume = {4}, year = {2017}, } @misc{9853, abstract = {Egg laying rates and infection loads of C. obscurior queens}, author = {Giehr, Julia and Grasse, Anna V and Cremer, Sylvia and Heinze, Jürgen and Schrempf, Alexandra}, publisher = {The Royal Society}, title = {{Raw data from ant queens increase their reproductive efforts after pathogen infection}}, doi = {10.6084/m9.figshare.5117788.v1}, year = {2017}, } @article{953, abstract = {The role of natural selection in the evolution of adaptive phenotypes has undergone constant probing by evolutionary biologists, employing both theoretical and empirical approaches. As Darwin noted, natural selection can act together with other processes, including random changes in the frequencies of phenotypic differences that are not under strong selection, and changes in the environment, which may reflect evolutionary changes in the organisms themselves. As understanding of genetics developed after 1900, the new genetic discoveries were incorporated into evolutionary biology. The resulting general principles were summarized by Julian Huxley in his 1942 book Evolution: the modern synthesis. Here, we examine how recent advances in genetics, developmental biology and molecular biology, including epigenetics, relate to today's understanding of the evolution of adaptations. We illustrate how careful genetic studies have repeatedly shown that apparently puzzling results in a wide diversity of organisms involve processes that are consistent with neo-Darwinism. They do not support important roles in adaptation for processes such as directed mutation or the inheritance of acquired characters, and therefore no radical revision of our understanding of the mechanism of adaptive evolution is needed.}, author = {Charlesworth, Deborah and Barton, Nicholas H and Charlesworth, Brian}, journal = {Proceedings of the Royal Society of London Series B Biological Sciences}, number = {1855}, publisher = {Royal Society}, title = {{The sources of adaptive evolution}}, doi = {10.1098/rspb.2016.2864}, volume = {284}, year = {2017}, } @article{22470, abstract = {A large variability (35–90%) in the ratio of transpiration to total evapotranspiration (referred here as T:ET) across biomes or even at the global scale has been documented by a number of studies carried out with different methodologies. Previous empirical results also suggest that T:ET does not covary with mean precipitation and has a positive dependence on leaf area index (LAI). Here we use a mechanistic ecohydrological model, with a refined process-based description of evaporation from the soil surface, to investigate the variability of T:ET across biomes. Numerical results reveal a more constrained range and higher mean of T:ET (70 ± 9%, mean ± standard deviation) when compared to observation-based estimates. T:ET is confirmed to be independent from mean precipitation, while it is found to be correlated with LAI seasonally but uncorrelated across multiple sites. Larger LAI increases evaporation from interception but diminishes ground evaporation with the two effects largely compensating each other. These results offer mechanistic model-based evidence to the ongoing research about the patterns of T:ET and the factors influencing its magnitude across biomes.}, author = {Fatichi, Simone and Pappas, Christoforos}, issn = {1944-8007}, journal = {Geophysical Research Letters}, number = {13}, pages = {6795--6803}, publisher = {American Geophysical Union}, title = {{Constrained variability of modeled T:ET ratio across biomes}}, doi = {10.1002/2017gl074041}, volume = {44}, year = {2017}, } @article{557, abstract = {PURPOSE. Gene therapy of retinal ganglion cells (RGCs) has promise as a powerful therapeutic for the rescue and regeneration of these cells after optic nerve damage. However, early after damage, RGCs undergo atrophic changes, including gene silencing. It is not known if these changes will deleteriously affect transduction and transgene expression, or if the therapeutic protein can influence reactivation of the endogenous genome. METHODS. Double-transgenic mice carrying a Rosa26-(LoxP)-tdTomato reporter, and a mutant allele for the proapoptotic Bax gene were reared. The Bax mutant blocks apoptosis, but RGCs still exhibit nuclear atrophy and gene silencing. At times ranging from 1 hour to 4 weeks after optic nerve crush (ONC), eyes received an intravitreal injection of AAV2 virus carrying the Cre recombinase. Successful transduction was monitored by expression of the tdTomato reporter. Immunostaining was used to localize tdTomato expression in select cell types. RESULTS. Successful transduction of RGCs was achieved at all time points after ONC using AAV2 expressing Cre from the phosphoglycerate kinase (Pgk) promoter, but not the CMV promoter. ONC promoted an increase in the transduction of cell types in the inner nuclear layer, including Müller cells and rod bipolar neurons. There was minimal evidence of transduction of amacrine cells and astrocytes in the inner retina or optic nerve. CONCLUSIONS. Damaged RGCs can be transduced and at least some endogenous genes can be subsequently activated. Optic nerve damage may change retinal architecture to allow greater penetration of an AAV2 virus to transduce several additional cell types in the inner nuclear layer.}, author = {Nickells, Robert and Schmitt, Heather and Maes, Margaret E and Schlamp, Cassandra}, issn = {0146-0404}, journal = {Investigative Ophthalmology and Visual Science}, number = {14}, pages = {6091 -- 6104}, publisher = {Association for Research in Vision & Ophthalmology}, title = {{AAV2 mediated transduction of the mouse retina after optic nerve injury}}, doi = {10.1167/iovs.17-22634}, volume = {58}, year = {2017}, } @article{22489, abstract = {The performance of urban drainage systems is typically examined using hydrological and hydrodynamic models where rainfall input is uniformly distributed, i.e., derived from a single or very few rain gauges. When models are fed with a single uniformly distributed rainfall realization, the response of the urban drainage system to the rainfall variability remains unexplored. The goal of this study was to understand how climate variability and spatial rainfall variability, jointly or individually considered, affect the response of a calibrated hydrodynamic urban drainage model. A stochastic spatially distributed rainfall generator (STREAP – Space-Time Realizations of Areal Precipitation) was used to simulate many realizations of rainfall for a 30-year period, accounting for both climate variability and spatial rainfall variability. The generated rainfall ensemble was used as input into a calibrated hydrodynamic model (EPA SWMM – the US EPA's Storm Water Management Model) to simulate surface runoff and channel flow in a small urban catchment in the city of Lucerne, Switzerland. The variability of peak flows in response to rainfall of different return periods was evaluated at three different locations in the urban drainage network and partitioned among its sources. The main contribution to the total flow variability was found to originate from the natural climate variability (on average over 74 %). In addition, the relative contribution of the spatial rainfall variability to the total flow variability was found to increase with longer return periods. This suggests that while the use of spatially distributed rainfall data can supply valuable information for sewer network design (typically based on rainfall with return periods from 5 to 15 years), there is a more pronounced relevance when conducting flood risk assessments for larger return periods. The results show the importance of using multiple distributed rainfall realizations in urban hydrology studies to capture the total flow variability in the response of the urban drainage systems to heavy rainfall events.}, author = {Peleg, Nadav and Blumensaat, Frank and Molnar, Peter and Fatichi, Simone and Burlando, Paolo}, issn = {1607-7938}, journal = {Hydrology and Earth System Sciences}, number = {3}, pages = {1559--1572}, publisher = {Copernicus Publications}, title = {{Partitioning the impacts of spatial and climatological rainfall variability in urban drainage modeling}}, doi = {10.5194/hess-21-1559-2017}, volume = {21}, year = {2017}, } @article{1078, abstract = {One of the key questions in understanding plant development is how single cells behave in a larger context of the tissue. Therefore, it requires the observation of the whole organ with a high spatial- as well as temporal resolution over prolonged periods of time, which may cause photo-toxic effects. This protocol shows a plant sample preparation method for light-sheet microscopy, which is characterized by mounting the plant vertically on the surface of a gel. The plant is mounted in such a way that the roots are submerged in a liquid medium while the leaves remain in the air. In order to ensure photosynthetic activity of the plant, a custom-made lighting system illuminates the leaves. To keep the roots in darkness the water surface is covered with sheets of black plastic foil. This method allows long-term imaging of plant organ development in standardized conditions. }, author = {Von Wangenheim, Daniel and Hauschild, Robert and Friml, Jirí}, journal = {Journal of Visualized Experiments}, number = {119}, publisher = {MyJove Corporation}, title = {{Light sheet fluorescence microscopy of plant roots growing on the surface of a gel}}, doi = {10.3791/55044}, volume = {2017}, year = {2017}, } @misc{5565, abstract = {One of the key questions in understanding plant development is how single cells behave in a larger context of the tissue. Therefore, it requires the observation of the whole organ with a high spatial- as well as temporal resolution over prolonged periods of time, which may cause photo-toxic effects. This protocol shows a plant sample preparation method for light-sheet microscopy, which is characterized by mounting the plant vertically on the surface of a gel. The plant is mounted in such a way that the roots are submerged in a liquid medium while the leaves remain in the air. In order to ensure photosynthetic activity of the plant, a custom-made lighting system illuminates the leaves. To keep the roots in darkness the water surface is covered with sheets of black plastic foil. This method allows long-term imaging of plant organ development in standardized conditions. The Video is licensed under a CC BY NC ND license. }, author = {Von Wangenheim, Daniel and Hauschild, Robert and Friml, Jirí}, publisher = {Institute of Science and Technology Austria}, title = {{Light Sheet Fluorescence microscopy of plant roots growing on the surface of a gel}}, doi = {10.15479/AT:ISTA:66}, year = {2017}, } @article{825, abstract = {What data is needed about data? Describing the process to answer this question for the institutional data repository IST DataRep.}, author = {Petritsch, Barbara}, issn = {1022-2588}, journal = {Mitteilungen der Vereinigung Österreichischer Bibliothekarinnen und Bibliothekare}, number = {2}, pages = {200 -- 207}, publisher = {Vereinigung Österreichischer Bibliothekarinnen und Bibliothekare}, title = {{Metadata for research data in practice}}, doi = {10.31263/voebm.v70i2.1678}, volume = {70}, year = {2017}, } @article{1162, abstract = {Selected universal experimental properties of high-temperature superconducting (HTS) cuprates have been singled out in the last decade. One of the pivotal challenges in this field is the designation of a consistent interpretation framework within which we can describe quantitatively the universal features of those systems. Here we analyze in a detailed manner the principal experimental data and compare them quantitatively with the approach based on a single-band model of strongly correlated electrons supplemented with strong antiferromagnetic (super)exchange interaction (the so-called t−J−U model). The model rationale is provided by estimating its microscopic parameters on the basis of the three-band approach for the Cu-O plane. We use our original full Gutzwiller wave-function solution by going beyond the renormalized mean-field theory (RMFT) in a systematic manner. Our approach reproduces very well the observed hole doping (δ) dependence of the kinetic-energy gain in the superconducting phase, one of the principal non-Bardeen-Cooper-Schrieffer features of the cuprates. The calculated Fermi velocity in the nodal direction is practically δ-independent and its universal value agrees very well with that determined experimentally. Also, a weak doping dependence of the Fermi wave vector leads to an almost constant value of the effective mass in a pure superconducting phase which is both observed in experiment and reproduced within our approach. An assessment of the currently used models (t−J, Hubbard) is carried out and the results of the canonical RMFT as a zeroth-order solution are provided for comparison to illustrate the necessity of the introduced higher-order contributions.}, author = {Spałek, Jozef and Zegrodnik, Michał and Kaczmarczyk, Jan}, issn = {2469-9950}, journal = {Physical Review B}, number = {2}, publisher = {American Physical Society}, title = {{Universal properties of high temperature superconductors from real space pairing t-J-U model and its quantitative comparison with experiment}}, doi = {10.1103/PhysRevB.95.024506}, volume = {95}, year = {2017}, } @article{995, abstract = {Recently it was shown that an impurity exchanging orbital angular momentum with a surrounding bath can be described in terms of the angulon quasiparticle [Phys. Rev. Lett. 118, 095301 (2017)]. The angulon consists of a quantum rotor dressed by a many-particle field of boson excitations, and can be formed out of, for example, a molecule or a nonspherical atom in superfluid helium, or out of an electron coupled to lattice phonons or a Bose condensate. Here we develop an approach to the angulon based on the path-integral formalism, which sets the ground for a systematic, perturbative treatment of the angulon problem. The resulting perturbation series can be interpreted in terms of Feynman diagrams, from which, in turn, one can derive a set of diagrammatic rules. These rules extend the machinery of the graphical theory of angular momentum - well known from theoretical atomic spectroscopy - to the case where an environment with an infinite number of degrees of freedom is present. In particular, we show that each diagram can be interpreted as a 'skeleton', which enforces angular momentum conservation, dressed by an additional many-body contribution. This connection between the angulon theory and the graphical theory of angular momentum is particularly important as it allows to systematically and substantially simplify the analytical representation of each diagram. In order to exemplify the technique, we calculate the 1- and 2-loop contributions to the angulon self-energy, the spectral function, and the quasiparticle weight. The diagrammatic theory we develop paves the way to investigate next-to-leading order quantities in a more compact way compared to the variational approaches.}, author = {Bighin, Giacomo and Lemeshko, Mikhail}, issn = {2469-9950}, journal = {Physical Review B}, number = {8}, publisher = {American Physical Society}, title = {{Diagrammatic approach to orbital quantum impurities interacting with a many-particle environment}}, doi = {10.1103/PhysRevB.96.085410}, volume = {96}, year = {2017}, }